Which TCP port should you open on the firewall?

Your network connects to the Internet by using a firewall. The perimeter network contains a Lync Server 2010 Edge Server. Some users work remotely.
You need to ensure that the remote users can sign in to Microsoft Lync 2010.
Which TCP port should you open on the firewall?

A.
80

B.
443

C.
4443

D.
5060

Explanation:
http://social.technet.microsoft.com/Forums/en-US/ocsaddressbook/thread/3fe9e121-a63a-4a56-a94b-312ebab1c05a